This is so I can crush a second bowl without the bias from the first bowl?

But imagine instead of keep adding ice, The coolant goes back-and-forth between solid and liquid It would be a powered refrigerator instead of a passive refrigerator

TLDR:

Instead of liquid to gass cooling you can probably do solid to liquid cooling.

The problem is not the cuddling it's that you feel like you cannot say no to the cuddling If you wanted to.

This can be complicated I think a rule of thumb is

When your sister asks to cuddle do you feel obligated to or do you feel preassured that you are not allowed to say no.

If it is like she is asking and you are endulging her need for a hugs then it is probably fine.

Where the line is for the physical emotional exclusivity that belongs only to your gf and your relationship is something you will have to negotiate.

What do you think?

Ask your gf what does being too close to my sister means?